Cork composition and products made therefrom



Aug. 21, 1945. A. H. WARTH ETAL 2,333,095

CORK COMPOSITIQN AND PRODUCTS MADE THEREFROM I Filed Aug. 3, 1942 371511 Raul Gr bw Jr.

Patented Aug. 1 21, 1945 CORK COMPOSITION AND PRODUCTS MADETHEREFBOMAlbin H. Warth and Paul Grabus, Jr., Baltimore, Md., assignors to CrownCork & Seal Company, Inc., Baltimore, Md., a corporation of New Y k AApplication August s, 1942, Serial No. 453,462

15 Claims. (01. 215-40) The present invention relates to a newcomposition of matter, adapted for use as a gasket or sealing materialof generalutility. More particularly, the invention relates to a newcomposition;

of matter adapted to serveas a substitute for cork compositions ofthetype extensively used, forinstance, in bottle caps of the crown type,a the sealing disc or cushion liner therein. In view of cation andclaims.

of hollyhock, such as is referred to in the specifi- Although thispithdoes not have the gas imperviousness ofnatural cork, its cell structureresembles cork somewhat, and the material is compressible and somewhatelastic in all directions. ,Zl'he hollyhock pith is considerably softerthan cork and, by itself, does not have suflicient strength, body,and-imperviousness to the scarcity at the present time of cork andrubher, it has become important to develop materials capable of servingas substitutes. Materials having the characteristics of cork, as tolightness,

compressibility, resilience, and gas imperviousness, however, areextremely rare or non-existent, and, prior to the present invention, nocompletely satisfactory substitute for, the standard cork compositiondiscs for crown closures has been disccovered. a K The cell structure ofnatural cork is funda mentally diiierent from practically all otherwoods or vegetable substances, since the cells have, theoretically,fourteen facets and have the characteristics of a spheroid, equallybalanced in all directions. Hence, cork is substantially equallycompressible in all directions,,wher'eas practically all other woods aremore compressible transversely of the grain than lengthwise. Because ofthese characteristics, cork may be, and conventionally is, granulated,mixed with a binder, treated by heat, and sliced into sheets or discs toserve as cushion liners for receptacle closures. In such discs, therelativepositions of the granules are immaterial, since the granuleshavesubstantially equal compressibility and resiliency in all directions.

Practically all other vegetable materials, however, are grainy, stringy,or have a substantial fiber content, whichmake them less compressible ina lengthwise direction than transversely. Hence, when such materials arecomminuted or granulated and mixed with a binder, someiof the particlesare so positioned as to be less compressible than others, with theresult that the sealing pad has varying characteristics as tocompressibility, resiliency, and sealing efllciency overdifferentportions ofits surface. An exception to this. general rule occurs inthecase of the pith ofuthe stem of the common hollyhock plant] gllollyhock,is known in various sections of the country by different names, such asHibiscus coccineus, Walt, ""Hibiscus moscheutos,"frequentlydesignated"as seahollyhock,"

"Althaea rosea which is of the cultivatedtype serve, in granulated form,with a binder as a satisfactory cork composition substitute forreceptacle closures and the like. It has been discovered, however, thatthis granulated material, when properly treated as described below, mayserve as a filler or extender in cork compositions and, may be employedto replace substantially by volume of the corkgranules, thus making itpossible, in commercial practice, to make a given amount of cork gosubstantially twice as far as heretofore in providingsealing discs forreceptacle closures;

An object of the invention, therefore, isto produce a corkcompositionhaving substantially all r of the characteristics of standardcompositions of the prior art, but employing a lesser amount of corkgranules. Totlfis end, the invention aims to conserve the supply ofnatural cork, by diminishing the amount employed ina given volume of thenew composition. i

A further object of the invention is toreduce the cost of corkcompositions,bysubstituting for a portion 01' the natural cork, normallyemployed, a cheaper material. a a 1' a I A further object of theinvention is to produce .a cork composition that cannotbe distinguishedand Sidalcea"malvdeflora knownto California as the wild hollyhock; theforegoing are typical position cushion ,discs substantially, 11

by casual inspection from the standard cork compositions heretoforeemployed. To this end,

the invention provides a for dyeing the substitute material to match thecork, whereby the substitute material is substantially indistinguishablein the finished product from the natural cork.

A further object of the invention is toincrease the impermeability ofnormally porous material mixed with granulated cork, so as tomake thefinished product substantially as imperviousto gases as prior artcompositions, or at least to make the finished product sumcientlyimpervious to gases as to satisfy commercial requirements.

A further object of the invention is to provide means; for renderingrelatively perviousycork com- Other and further, obje 'ts and, adantages of the invention wint e pp r nt-th ngs skilled in the :art, froma consideration ofthe ri'ollowingldescripti o specific emwd fii etf t,ilef ei tion.

In the drawing:

Figure 1 is a diagrammatic plan view of a cushion disc for a crownclosure. made from the cork composition of the present invention. withthe pith granules in {heir natural. non-dyed state:

Figure 2 is a similar diagrammatic view with the pith granules indicatedas having been dyed to match the cork granules:

Figure 3 is a. bottom plan view of a crown closure in accordance withthe present invention. and

Figure 4 is a diametric section taken on line 4-4 of Figure 3.

In carrying out the invention of the present application, hollyhock stemraw material. is gathered from areas where it grows in great abundance,such as in certain sections of Florida. This raw material has a longfibrous, gray bark of extreme thinness. similar to tissue paper. Thestems are decorticated by stripping or peeling off the bark which onlylightly adheres to the internal pith. in a Ball & Jewel mill, in thesame manner that cork is conventionally ground. If the moisture contentof the stem material is at the optimum, between 5 and 6%, there is verylittle loss in grinding, whereas if the material is bone-dry, the lossis greater. Therefore, it is desirable to control the moisture contentprior to the grinding operation, for instance, by wetting. if themoisture content is unduly low. Since the hollyhock stems contain noneof the dirt, bark dust, and other impurities that are prevalent withcork, the grinding loss is less than with cork in ordinary millingoperations.

The ground hollyhock material has adensity much less than cork, i. e.,about .1085, as compared with .25-.20 for cork. As stated above. it hasa cellular structure. rather than being of fibrous nature and issubstantially equally compressible in all directions. It is softer andmore compressible than cork, but this disadvantage can be overcomebytreating the granulated pith in suitable ways. such as by impregnatingthe particles with a thin glue solution containing a wetting agent.Penetratio or impregnation of the particles causes their density toapproach that oi cork and decreases their compressibility.

In order to improve the appearance of the finished product, it isdesirable to dye the granulated pith, since the material in the naturalstate is substantially white or light gray in color. Any dyes, such asthose employed in the manufacture of artificial chocolate or certainextracts from coffee beans, may be employed. A certified color dye knownas chocolate'brown, of the National Analine 8: Chemical Co. has beenfound to be entirely satisfactory for this purpose.

Preferably, the dye is incorporated in the thin glue solution used toimpregnate the hollyhock particles. Asuitable formula for this purposeis as follows: A

Parts Water 50 Gelatin Glycerine Tan color 1 Aerosol 1 The pith is thenground or granulated penetrate the hollyhock particles, carrying the tandye along, imparting to the particles on appearance similar to cork.

After such treatment with the impre nating agent and the dye, the pithparticles are air dried and then thoroughly mixed with the previouslyground cork granules. The glue binder may then be added, while the pithand cork particles are tumbling in a dough mixer. The resulting productmay be packed into rods or blocks or roll molds and subjected to theusual heat treatment. to set the glue binder. After a suitable seasoningperiod. the cushion discs may be sliced from the rod or sheets cut fromthe roll or block in the usual manner. Oi" course. any other knownmethod of making, the liners or gaskets may be employed, substitutingthe mixture of treated pith particles, granulated cork particles. andglue for the usual granulated cork products alone.

A suitable formula for the binder. employed to secure the hollyhock pithparticles and the cork particles together is as follows:

Parts Water 31 Gelatin 22 Sulphonated oil l5 Glycerine 30 Paraffin wax 2if hexamethylenetetramine is used, about three times that amount shouldbe added.

Approximately 1 part of binder is added to 2 parts of the preparedhollyhock and cork mixture in the dough mixer to produce the agglomeratcfor packing, although the amount can be varied, to satisfy particularconditions.

The following formula is suitable for ribbon or sheet blocks or rolls:

Parts Cork (granulated in roller mill) 50 Decorticated hollyhock stems(Ball & Jewel Mill granulated, thin glue processed) 33 Cold glue mix 31Sulphonated castor oil 5 Insolubilizing agent (1 parthexamethylenetetramine, 2 parts water 2 ,4

, The invention is not limited to specific proportions of pith and corkgranules. It has been found that, in general, a proportion of 50% pithand 50% cork by volume is quite satisfactory and produces an efiectivesealing pad, capable of withstanding a gas pressure of 70 pounds persquare inch, without the use of a center spot liner or other gasimpervious layers or coatings. When cork and pith granules are mixed inthe proportion of 25 pounds of cork to 15 pounds of hollyhock pith, thevolumes of the two materials will be substantially equal andsatisfactory sealing pads can be produced.

In the accompanying drawing, a sealing pad is indicated generally at I0,the cork granules being shown at H and the hollyhock pith granules atl2; Although the invention is not limited to any particular relation ofparticle sizes. it is preferred that all of the granules be ground tosubstantially the same average size, such as those that will passscreens having eight openings and twelve openings to the inch. The pithgranules l2 in Figure 1 are shown in their netura-l, non-dyed conditionand appear in the finished product as substantially white or light grayspots. If this is objectionable, the particles may be dyed as indicatedin Figure 2. so that the pith particles I substantially match thecorkparticles IS in the disc l4.

As indicated in Figures 3 and 4, a center spot liner 2!) may beadhesively united to the exposed face of the cushion disc 2 I, inconcentric relation to the crown closure 22, as is well understood inthe art. The spot liner may be of any of the resin-wax composition, toincrease the gas imperviousness of the disc as a whole by sealing thesurface cells of the hoilyhock pith granules. The pith of other plantsmay be substituted cork and granulated hoilyhock pith in substantiallyequal volumes, and a binder.

7. A cushion disc adapted for use as a sealing pad in a receptacleclosure comprising substantially equal volumes or granulated cork andgranulated hoilyhock stem pith, and a binder, the cork and pith granulesbeing of substantially the same average size.

8. A cushion disc adapted for use as a sealing pad. in a receptacleclosure comprising granulated cork, granulated hoilyhock pithimpregnated with glue to decrease its porosity, and a binder.

9. A resilient, substantially gas-impervious sealing disc ioruse in areceptacle closure comprising granulated hollyh'ock pith, the particlesof which are impregnated with a cell-sealing agent to decrease theirporosity, granulated cork, and

a binder. I

10. A resilient, substantially gas-impervious sealing disc for areceptacle closure comprising particles ofgranulated hoilyhock pithpre-coated with glue to decrease their porosity, granulated for thehoilyhock pith for certain purposes, al-

though not as satisfactory for other purposes. The pith oisuniiowerstalk and similar plants has proved satisfactory in cases where equal0031-, pressibility of the particles in all directions is not essential.

It must be understood, therefore, that the'invention contemplates allvariations and changes coming within the scope oi. the appended-claimsand their equivalents.

We claim: l. A cork composition comprising cork granules, pith granulesfrom hoilyhock of the Florida type known as Hibiscus coccincus, Walt.inter mixed therewith, and a binder.

2. A cork composition comprising substantially 50% each by volume ofgranulated cork and granulated pith from hoilyhock of the Florida typeknown as Hibiscus coccineus, Walt. and a binder.

3. A cork composition comprising granulated cork and granulatedhollyh'ock pith material, and a binder.

4. A cork composition comprising equal volumes of granulated cork andgranulated hollyhock pith material.

5. A cushion disc adapted for use as a sealing pad in a receptacleclosure or the like, comprising granulated cork, granulated hollyhockpith, and a binder.

6. A cushion disc adapted for use as a sealing pad in a receptacleclosure comprising granulated cork particles intermixed therewith, and abinder uniting the corkand pith granules.

i 11. A cork composition comprising granulated cork, granulatedhoilyhock pith dyed a color to match the cork granules, and a binder.

12. A cork composition comprising granulated cork, granulated hoilyhockpith, the particles of which have been dyed to match the cork andporosity, and a binder.

have been pre-treated with glue to decrease their 13. A cork compositioncomprising granulated cork and granulated hoilyhock stem pith insubstantially equal volumes, the pith granules being characterized bythe presence of suflicient brown dye to substantially match the cork, bya cellsubstantially sealing agent which decreases their porosity, and

by being of thesame average size as the cork particles.

14. A receptacle closure having secured therein a cork compositioncushion liner comprising granulated cork, granulated h'ollyhockpith, anda binder.

15. In combination, a cap of the crown type, a cushion liner thereforcomprising substantially equal volumes of granulated cork and granulatedhoilyhock pith material, and a center s t of gasimpervious sheetmaterial adhesively united to the exposed i ace of the liner.

mm H. wsa'rn. PAUL owns, an.

